In addition to being applied to the medical field for checking a health condition of a specific part of a human body, an ultrasonic inspection technology is further used as a nondestructive testing technology (Non Destructive Testing, NDT) which is widely applied to various industrial fields. The industry has invented various “industrial ultrasonic nondestructive flaw detector” or “industrial ultrasonic detector” that are used to detect “a health condition” of surfaces or interiors of various to-be-detected workpieces or objects, so as to detect whether an internal break or crack occurs in the workpieces. For example, an invention application of the United States field with the application Ser. No. 13/658,841 on Oct. 24, 2012 and entitled “ROTATING ULTRASONIC DETECTING APPARATUS WITH HYDRAULIC LIFT UNIT” discloses an industrial-use ultrasonic inspection system, which is referenced herein.
A typical ultrasonic inspection system includes at least one ultrasonic probe and a workpiece holding apparatus. During inspection performed on a to-be-detected workpiece, the workpiece holding apparatus moves the to-be-detected workpiece to a proper location, starts the ultrasonic probe to transmit an ultrasonic wave to the to-be-detected workpiece, enables the transmitted ultrasonic wave to be conducted, through a liquid acoustic transmission medium (such as water), to the to-be-detected workpiece, receives a return ultrasonic wave that is still conducted to the ultrasonic probe through a liquid acoustic transmission medium after being reflected by the to-be-detected workpiece, and performs a specific image processing algorithm to processes the received return ultrasonic wave, so as to construct an ultrasonic image of the to-be-detected workpiece. The ultrasonic reflected by a break or crack location significantly changes, and therefore the ultrasonic image constructed through observation can determine various defects in the to-be-detected workpiece.
In specific application occasions, a lifting device needs to be designed to flexibly lift or drop to-be-detected workpieces to different heights, so that the ultrasonic probe can be conveniently used to perform ultrasonic inspection on the to-be-detected workpieces. A detect that exists in an existing lifting device is that a shape of a workpiece bearing mechanism changes under a function of weight of the workpiece bearing mechanism, which causes interference (or deadlock) between the workpiece bearing mechanism and a guide pillar, and therefore the to-be-detected workpiece cannot move up and down under a function of a power driving system to perform normal ultrasonic inspection.